使用 azure appsettings 读取 azure webjob 中 EventHubTrigger 的连接字符串

Question

I am writing a azure webjob using.Net core 3.1 and reading the events from eventhub. I have been able to get this working locally where I read all settings from local appsettings.json and appsettings.dev.json. public async Task ProcessEvent([EventHubTrigger("%EventHubName%", Connection = "EventHubConfigConnectionString", ConsumerGroup = "%ConsumerGroupName%")] EventData eventData)

However, I now tried using the azure appservice appsettings to store the connection string where the app settings are exposed as environment variables, which I am adding to the configuration as: Configuration = new ConfigurationBuilder().AddEnvironmentVariables().Build();

But I still get the error: System.ArgumentNullException: Value cannot be null. (Parameter 'connectionString') at Microsoft.Azure.EventHubs.Primitives.Guard.ArgumentNotNullOrWhiteSpace(String argumentName, String value) System.ArgumentNullException: Value cannot be null. (Parameter 'connectionString') at Microsoft.Azure.EventHubs.Primitives.Guard.ArgumentNotNullOrWhiteSpace(String argumentName, String value)

I verified that the variable names are the same. I read online and looks like the connection string to the EventHubTrigger has to be present in appsettings file and not in environment variable?

Am I missing something?

Answer 1

You should have an entry in your appSettings.json file, I would say under the connectionStrings section like below:

{
  "AppInsights_InstrumentationKey": "",
  "ConnectionStrings": {
    "EventHubConfigConnectionString": ""
  }
}

I think in the Azure portal, for your app service, you can set a new connection string with the name EventHubConfigConnectionString which will override the one that is in your appSettings.json file:

Then in your Program.cs have the following maybe:

Configuration = new ConfigurationBuilder()
                    .SetBasePath(Environment.CurrentDirectory)
                    .AddJsonFile("appSettings.json", optional: true)
                    .AddEnvironmentVariables()
                    .Build();

Hope this helps.